Design and Fabrication of a Portable 1-DOF Robotic Device for Indentation Tests

There are many tactile devices for indentation examinations to measure mechanical properties of tissue. The purpose of this paper is to develop a portable indentation robotic device to show its usability for measuring the mechanical properties of a healthy abdominal tissue. These measurements will help to develop suitable mathematical models representing abdominal tissue. A 1-DOF portable robotic device has been designed to be placed on the patient’s body. The device presses sensor plate on the abdomen. Force and position sensors measure the indentation force and displacement, respectively. Due to tissue time-dependent behavior, linear viscoelastic models with three, five and seven parameters have been selected for mathematical modeling. Nonlinear Least Squares (NLS) method is adopted to fit viscoelastic models with experimental data obtained from stress relaxation tests. Using Finite Prediction Error (FPE) criterion, viscoelastic model with five parameters has been selected as the optimal model. The results of the present paper can be used in abdominal tissue simulators to facilitate teaching palpation examinations.